(1) Field of the Invention
The present invention relates to a method for reserving network resources for pseudo point-to-point connections by means of an idempotent resource reservation protocol.
(2) Description of Related Art
Examples of idempotent resource reservation protocols are Resource reservation Protocol (RSVP) as initially defined in Request For Comment (RFC) 2205 published by the Internet Engineering Task Force (IETF) in September 1997, or Resource reSerVation Protocol—Traffic Engineering (RSVP-TE) as initially defined in RFC 3209 published by the IETF in December 2001, that is to say an extension to RSVP for Label Switched Paths (LSP) such as Multi-Protocol Label Switching (MPLS) paths, or RSVP-TE Extensions for Generalized Multi-Protocol Label Switching (GMPLS) as initially defined in RFC 3473 published by the IETF in January 2003, that is to say an extension to RSVP for time-division switching such as Synchronous Optical Network (SONET), Synchronous Digital Hierarchy (SDH), wavelength (optical lambdas), and spatial switching such as incoming port/fiber to outgoing port/fiber.
Examples of pseudo point-to-point connections are Pseudo wires (PW) as defined in RFC 3985 published by the IETF in December 2005, or Multi Segment—Pseudo wires (MS-PW) as defined in Internet draft draft-ietf-pwe3-dynamic-ms-pw-02.txt entitled “Dynamic Placement of Multi Segment Pseudo wires” and posted on the IETF web site in October 2006.
PW emulates Frame Relay, ATM, Ethernet, Time Division Multiplexing (TDM), or SONET/SDH point-to-point connections (or wires) across a Packet Switched network (PSN).
The behavior and characteristics of the native service are emulated by means of the following functions:
encapsulation of bit streams, cells, or packets arriving at an ingress port (logical or physical),
carriage of the encapsulated data across a PSN tunnel, such as an MPLS path, a Layer 2 Tunneling Protocol (L2TP) tunnel, etc,
establishment of the PW, including the exchange and/or distribution of the PW identifiers used by the PSN tunnel endpoints,
managing the signaling, timing, order, or other aspects of the native service at the boundaries of the PW,
service-specific status and alarm management.
Provider Edge equipment (PE) provide Customer Edge equipment (CE) with the emulated native service via an Attachment Circuit (AC). An AC denotes a physical or virtual circuit attaching a CE to a PE such as a Frame Relay DLCI, an ATM VPI/VCI, an Ethernet port, a virtual Local Area Network (VLAN), a Point-to-Point Protocol (PPP) connection on a physical interface, an MPLS LSP, etc.
PEs accommodate the following data plane functions:
Native Service Processing (NSP), that is to say processing of the data received by the PE from the CE before presentation to the PW for transmission across the PSN, or processing of the data received from a PW by a PE before it is output on the AC,
Forwarder (FWRD), that is to say selection of the PW to use in order to transmit a payload received on an AC.
The following signaling mechanisms are further required:
end-to-end signaling between the CEs, such as Frame Relay Permanent virtual Circuit (PVC) status signaling, ATM Switched virtual Circuit (SVC) signaling, TDM Circuit Associated Signaling (CAS), etc,
PW maintenance between the PEs to set up, maintain, and tear down PWs, including any required coordination of parameters,
PSN tunnel signaling to control the PW multiplexing and some elements of the underlying PSN, such as L2TP control protocol, MPLS Label Distribution Protocol (LDP), or RSVP-TE.
There is a requirement for service providers to be able to extend the reach of PW across multiple PSN domains. A Multi-Segment PW (MS-PW) is defined as a set of two or more contiguous PW segments that behave and function end-to-end as a single PW.
For MS-PW support, PEs are further instantiated as terminating provider edge equipment (T-PE) and switching provider edge equipment (S-PE), the former being present in the first and last segments of a MS-PW and terminating the MS-PW via an AC, the latter inter-connecting PW segments of a MS-PW between different PSN domains.
T/S-PEs are exchanging MS-PWs resource reservation signaling (e.g., by means of RSVP-TE) so as they can appropriately select/establish the underlying PSN tunnels towards the next signaling hop and reserve the corresponding network resources.
The disclosed method is disadvantageous in the event of many MS-PWs terminating at a single head-end T-PE. Indeed, resource reservation sessions need to be maintained for each and every MS-PW, causing this head-end T-PE to be over-flooded with resource reservation signaling and states. This solution is clearly not scalable.